Flame suppressing arrester construction



Patented Dec. 27, 1949 UNITED STATES PATENT OFFICE FLAME SUPPRESSINGARRESTER CONSTRUCTION Ralph R. Pittman, North Little Rock, Ark.Application August 5, 1946,:Serial No.'688,571 6 Claims. (01. 175-30)This invention relates generally to devices suitable for limiting a risein voltage, such as might be caused by lightning or a switching surge,of a connected conductor by means of arc-gaps adapt: ed to spark over ata predetermined voltage, together with means for interrupting thepassage of current through the gaps following sparkover.

The objects of the present invention include the provision of aself-supportingarrester construction in which the supporting elementsare functional elements in the mechanism of are extinguishment; theprovision of means for confining, cooling and venting the gaseous flameattending the operation of a plurality of arresters of the expulsiontype: the provision of a simple structure adapted for applications inwhich a plurality of serially arranged expulsion arrester units is moreefiective than a single unit; and a construction including means forsuppressing noise of operation. Other objects will appear as thedescription proceeds.

It is now recognized that lightning discharge devices of the expulsiontype offer the best means now known for the dissipation of extraneousand superimposed high voltages which appear in electric circuitsoperating at sufficiently low voltage to permit effective areextinguishment in a single unit. Application of expulsion arresters forapparatus protection at higher voltages has been commerciallyuneconomical, for the reason that. both the dielectric and mechanicalstrength retherefore unsuitable for use in transporting the.

gas from a series circuit arrangement of several units to asingle vent,for reasons shortly to appear.

The invention comprises the elements and com binations thereof, featuresof construction and arrangement of parts exemplified in the drawing anddescription, and the scope of the invention will be indicated in theaccompanying claims.

"Fig. 1;of the drawing shows an elevational View of an embodiment of theinvention, partly in section, and Fig. 2 is a section taken along theline 2"2-rof"Fig. 1.

In'fietail, the supporting members 45 and 46 carry a hollowv cylindricexhaust chamber 29, of conducting material, to the top of which arerigidly-secured in spaced parallel upstanding relationship, bymeans ofthe cap screws 22, an expulsion lightning arrester .unit and a flamesuppressor, designatedrespectively in their entirety by. the referencecharacters l2 and I3. The intermediate exhaust chamber 21 is mounted ontherespectiveupper ends of the members l2 and I3, and has similarly.rigidly secured to its top another expulsion arrester and another flamesuppressor, and the upper exhaust chamber 24 is similarly mounted on thetop of the last-named arrester unit .and flame suppressor.

'Centrally positioned on the top of the upper exhaust chamber, isrigidly secured thereto by means of thecapscrews 22, an additionalexpulsion arrester unit. l5, extending upwardly therefrom toa point nearthe line electrode I0, to providethe usual leakage gap l'l therebetween.

The expulsion arrester units as here illustrated are similar to, anddescribed as to operation more in detail, in U. S.Patent No. 2,164,720dated July 4, 1939, granted to Ralph R. Pittman.

The expulsion arrester unit I5 includes the upstanding tubular insulatorl8, and has secured thereto by means of threaded engagement at itsrespective ends, thetop closure and upper conducting electrode 11, andthe lower conducting electrode 2|. The tubular insulator [8 contains theeccentrically. mounted filler 20, also of insulating material, whichpartially fills the bore of the tubular insulator. The lower electrode2| is provided with-an upward and internal extension I9, thearrangementbeing such that the weakest electrical path through thedevice is along the line of abutment of the filler 20 with the innersurface of, the tubular insulator l8, and between the upper end of theelectrode extension l9 and the upper electrode H. Following sparkover ofthe weakest electrical path, any are ensuing is driven around thefillerll'l and concurrently elongatedto facilitatearc.extinguishment.The openings v23 through the lower electrode 2! are positioned inregistration with the opening 25 through .the .top of the upperexhaustchamber 24, and the gaseous'flameattending operation of the device .isvented only into the .exhaust chamber. The device is economicallyconstructed when the tubularinsillatorlB ,and'filler 20 are formed of anarceresponsive volatilehmaterial, such as hard fiber.

The-expulsion arrester .units l2 differ from the unit l5 onlyinthamatter .ofjiorm of the respec- 'tive topclosures and upperelectrodes, the former being provided with a flanged upper electrode 26through which the cap screws 22 upwardly extend to rigidly secure thetop of the units to the respective lower surfaces of the exhaustchambers 24 and 21. In a manner similar to that described in connectionwith the expulsion arrester unit 15, the expulsion arrester units l2 arearranged to exhaust the gaseous flame attending operation respectivelythrough the openings 28 into the exhaust chambers 21 and 29.

A flame suppressor I3 is positioned in electrically parallelrelationship with each of the expulsion arrester units 12 between theadjacent ends of the exhaust chambers 24, 21 and 29. Each flamesuppressor l3 includes a longitudinally extending tubular insulator 33,to the respective ends of which are threadedly fitted the flanged andthe vented fitting 32 and 36. The latter fittings tightly engage therespective end surfaces of the exhaust chambers, and the vent openings35, in the upper fitting 32, and the vent openings 31, in the lowerfitting 36, are respectively arranged to register with the openings 3|respectively in the lower end of the exhaust chambers 24 and 21 and theopenings 38 respectively in the upper end of the exhaust chambers 21 and29, thereby providing an enclosed electrically insulated passageway incommunication with the interiors of the chambers 2d, 2'! and 29. Undercertain conditions, hereinafter mentioned, it may i be desirable tosupport a longitudinally extending cylindric element of insulatingmaterial 34, hav ing a diameter less than the inside diameter of thetubular insulator 33, within the latter. If so. the filler 34 may beprovided with upwardly and downwardly extending recesses at itsrespective ends, for registration with respectively correspondingupwardly and downwardly extending portions of the end fittings 32 and3t.

To provide a flame-suppressing passageway betightly fitted against thelower surface of the r exhaust chamber 29, and held in position by thescrews 22. Vent openings 42 communicate with the interior of the exhaustchamber 29 through a registering opening 30 through the bottom of thelatter, and the lower end of the tube is is threadedly fitted with theend fitting as, through which the vent openings 44 extend incommunication with the interior of the tube 40..

If the particular application of the construction is for the purpose oflimiting the rise of the conductor Hi to a predetermined magnitude aboveground potential, the lower exhaust chamber 29 is connected to ground,as indicated symbolically at 41. With such an arrangement, any voltagesufiiciently great to spark over the series arrangement of the externalgap II and the preferential spark gaps of the three serially arrangedexpulsion arrester units will cause operation of the arrester units.After sparkover, current passes serially from the electrode IQ via thespark gap H to the upper arrester unit l5, thence through anotherarrester unit l2 to the conducting exhaust chamber 21, thence throughanother arrester unit 12 to the conducting exhaust chamber 29, andthence to the ground 41.

' rester unit at current zero of an alternating ourrent circuit. Thedielectric strength of the gas passing from one exhaust chamber to theother through the intervening flame suppressor is dependent upon itstemperature, and that construction providing effective cooling is mostdesirable. For this reason, I prefer to first expand the gas in theexhaust chamber and then pass the gas through an annular path bounded byan insulating material which volatilizes when in contact with thegaseous flame. One such material is hard fiber. The evolution of watervapor from the fiber, along with gases, effectively cools the gaseousconducting flame, thereby maintaining the desired dielectric strength ofthe gas column.

A specific example of a flame suppressor which I have found to beefiective in preventing arc transfer embodies a tubular fiber insulatorhaving an internal diameter of 1 inch, and fiber filler in diameter,with a length between conducting members at the respective endsinternally of the tube of 4 inches. A flame suppressor so built issatisfactory for use in parallel with expulsion arrester units rated at9 kv. rms.

From inspection of the drawing, it may be seen that the upper flamesuppressor l3 conducts thegas evolved in the upper lightning arresterunit 15 from the exhaust chamber 24 to the exhaust chamber 27; that theintermediate flame suppressor l3 conducts both the gas passing throughthe upper flame suppressor and the gas evolvedin the operation of theupper arrester unit i2, and that the gas evolved in all three arresterunits is finally passed into the exhaust chamber 29. Electrically theoperation of the device, insofar asdanger from flashover outside of thearrester units is concerned, would be satisfactory if the gas and flamecollected in the chamber 29 was simply vented downwardly from itsbottom. However, the noise of operation is greatly reduced, and theflame cooled, if the lower exhaust chamber 29 is vented through a flamesuppressor 14. The dimensions stated above in connection with the flamesuppressors l3 are satisfactory for the flame 1. In combination, aplurality of expulsion arrester units including a line terminal arresterunit, a ground terminal arrester unit, and an intermediate arresterunit, each of said units. being closed at the upper end and vented atthe lower end, closed exhaust chambers of conduct ing materialelectrically connecting said arrester units in a serieacirauitlarzangement such that the vented end of said line terminal arrester unitfls connected through oneexhaustachamber to the closed end of theintermediate arrestenunit and the vented end of the internediate;arrester unit is connected through another exhaust chamber totheel'osed end of the ground terminal arrester unitmach -=exhaustchamber 1 having an opening therein through which conducting gas'isdischarged from the-vented end-'of the associated arrester unit intoeach exhaust chamber, and means including a tubular insulator joiningthe adjacent ends of said exhaust chambers in communication with theinteriors thereof, said insulator being rigidly fastened at itsrespective ends to the adjacent ends of said exhaust chambers andproviding the only path of egress for gas discharged from said lineterminal arrester unit and vent means for discharging gas from saidanother exhaust chamber to the atmosphere.

2. In combination, a plurality of expulsion arrester units including aline terminal arrester unit, an intermediate arrester unit, and a groundterminal arrester unit, each of said units being closed at the upper endthereof and vented at the lower end thereof, a first hollow exhaustchamber of conducting material mechanically joining and electricallyconnecting the vented end of said line terminal arrester unit to theclosed end of said intermediate arrester unit, a second hollow exhaustchamber mechanically joining and electrically connecting the vented endof said intermediate arrester unit to the closed end of said groundterminal arrester unit, said first exhaust chamber having an openingtherein in communication with the vented end of said line terminalarrester unit and said second exhaust chamber having an opening incommunication with the vented end of said intermediate arrester unit,flame-suppressing means joining the respective exhaust chambers incommunication with the respective interiors thereof, saidflame-suppressing means including a hollow tube of insulating materialarranged to transport the gaseous products attending operation of saidarrester units from one chamber to the other, said flame-suppressingmeans being constructed and arranged to cool the gaseous productspassing therethrough so as to preclude arc formation under theconditions of operation between said exhaust chambers, and vent meansfor discharging gaseous products from said second exhaust chamber to theatmosphere.

3. In a lightning arrester, in combination, spaced first and secondhollow conducting exhaust chambers, a first expulsion arrester unitmounted on the upper end of said first exhaust chamber and arranged todischarge conducting gaseous flame therein when operating, a secondexpulsion arrester unit spanning the space between the lower end of saidfirst chamber and the upper end of the second chamber and arranged todischarge conducting gaseous flame within the latter concurrently withthe discharge from said first expulsion arrester unit, flamesuppressingmeans mounted between said chambers in spaced parallel relationship withthe second arrester unit, said flame-suppressing means comprising ahollow tube of insulating material in communication at each end with therespective exhaust chambers and forming a passageway therebetween, thelength of said tube being so related to the cross-sectional area of thepassageway within the tube that are formation through said passagewayunder the conditions of operation is precluded, and vent meansconnecting said second mellow aexhaust :claam'ber eto titheatmoscixlntca'iightninge bination, a support, iaeventedtlowerchamber-01? conducting material {carried ith'ereby, tan :expul- 5. mmiightningiarrester 'R-mitand: arflame isuppressonmounted irrspaoedparallel-relationship on the top -.'of 'zsaid lower rchamber randextending upwa-rdly therefrom, an intermediate 1 chamber of conductingmater-ia'i amounted on the respective upperiendsmf iz'saidearrester:unit and said flame suppressor, an expulsion lightning arrester -unitand an 'iilame iswuppr-essor mounted in spaced parallel relationship onthe top of said intermediate chamber and extending upwardly therefrom,an upper chamber of conducting material mounted on the respective upperends of said last-named arrester unit and flame suppressor, and anexpulsion lightning arrester unit mounted on the top of said upperchamber and extending upwardly therefrom, each of the lightning arresterunits being vented only at the lower end thereof and each of saidchambers having an opening closed by the vented end of the associatedarrester unit through which gaseous products attending the operation ofsaid arrester units may discharge into the associated chamber, and eachof the flame suppressors including a tubular insulator vented at eachend and each of said chambers having an opening therethrough closed byand in registration with the respective vented ends of said flamesuppressors.

5. The combination with at least two expulsion lightning arrester unitseach closed at the upper end and each having a vent only at the lowerend for discharging conducting gas from the interior of said arresterunits, of a hollow exhaust chamber of conducting material having anopening in the top and an opening in the bottom thereof, means rigidlyfastening the phere.

rresterconstnuctiomin com vented end of one of said arresters to the topof said exhaust chamber in registration with the opening in the topthereof for closing said opening, means rigidly securing the closed endof another arrester unit to the bottom of said exhaust chamber, a hollowtubular insulator open at each end, means rigidly securing one end ofsaid tubular insulator to the bottom of said exhaust chamber inregistration with the opening therein for closing the last-namedopening, and a longitudinally extending element of insulating materialmounted within said tubular insulator and partially filling the borethereof for cooling gas passing therethrough, said exhaust chamberhaving an internal volume substantially greater than the unfilled spacewithin said tubular insulator.

6. In an expulsion lightning arrester construction, in combination, aplurality of exhaust chambers of conducting material disposed invertical spaced relationship, a plurality of lightning arrester units ofthe expulsion type each closed at the upper end and each having a ventonly at the lower end for discharging conducting gas from the interiorof said arrester units, said arrester units being rigidly secured inseries circuit relationship between said exhaust chambers, an opening ineach of said exhaust chambers closed by the lower end of each arresterunit through which conducting gas is downwardly discharged into theexhaust chamber immediately below each arrester unit, a hollow tubularinsulator rigidly secured at its respective ends to the adjacent ends ofsaid exhaust chambers mounted in spaced parallel relationship with said7 8 arrester units, openings in said exhaust chambers REFERENCES CITEDat sald respective ends closed by said respective ends for providing aclosed passageway between The following references are of record in thesaid exhaust chambers, an additional arrester file of t s Pa unitsecured in upstanding position to the top 5 TENT of the uppermostexhaust chamber, an opening UNITED STATES PA S in the top of the latterclosed by said additional u be Name Date arrester unit through whichconducting gas from ,1 7, it ma et a1 9, 3 said additional arrester maybe discharged down- 2,291,175 Stroup July 28, 1942 wardly into saiduppermost exhaust chamber, and 10 2,357,887 Goldner S p 1944means'venting the lowermost exhaust chamber to the atmosphere.

RALPH R. PI'I'I'MAN.

